This invention relates generally to an apparatus and process for pneumatically conveying loose or bulk material in dust or fine-grain form.
One form of pneumatic conveyor apparatus comprises (see for example German Offenlegungsschrift No. 27 03 736) a container for containing the material to be conveyed, with a material feed means in the upper region, and a conveyor nozzle in the lower region. Disposed at a spacing from the conveyor nozzle is a conveyor conduit into which material is entrained from the container by a flow of gas under pressure from the nozzle. A discharge control line is also introduced laterally into the container to provide further control in the conveying action, with pressure gas being introduced through the control line and flowing through part of the loose or bulk material, to entrain some of the material when the gas then flows out through the conveyor conduit. However, when the pressure gas is introduced into and flows through the material in the container, that can also result in the material being compacted, particularly when the direction of flow is downwards, and such compacting will almost invariably have a detrimental effect on the uniformity and regularity of the conveying action.